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gpu: nvgpu: prevent extra user unmaps

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It is possible that user space requests more unmaps on a buffer
than it requested maps
In this case, we end up dropping one extra refcount which could
lead to releasing buffer early

Fix this by checking and returning if buffer's user_mapped
refcount is already zero

Bug 200130521

Change-Id: Ic8ef2dbfe0476b16d852ad899b1ed0404b5bb7de
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/788904
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>
This commit is contained in:
Deepak Nibade
2015-08-27 12:17:07 +05:30
committed by Terje Bergstrom
parent dab594ac13
commit 5b4451cad8
1 changed files with 6 additions and 0 deletions
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6
drivers/gpu/nvgpu/gk20a/mm_gk20a.c
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@@ -873,6 +873,12 @@ static void gk20a_vm_unmap_user(struct vm_gk20a *vm, u64 offset,
mutex_lock(&vm->update_gmmu_lock);
}
if (mapped_buffer->user_mapped == 0) {
mutex_unlock(&vm->update_gmmu_lock);
gk20a_err(d, "addr already unmapped from user 0x%llx", offset);
return;
}
mapped_buffer->user_mapped--;
if (mapped_buffer->user_mapped == 0)
vm->num_user_mapped_buffers--;